In recent years, various electronic equipment has become small in size and light in weight, multifunctional, and highly functional, and high density has been demanded for electronic equipment to be mounted. In response to this demand, various electronic components manufactured as semiconductor devices have been increased. Furthermore, other than semiconductor devices manufactured as circuit elements, various sensors are also manufactured as semiconductor devices for decreasing the size and reducing the weight. For example, in an acceleration sensor or an angular velocity sensor having a small and simple structure by using MEMS (Micro Electro Mechanical Systems) technology, a mechanical quantity sensor or the like has been put into practical use, which is of a type in which a movable part moving according to an external force is formed on a semiconductor substrate and the displacement of this movable part is detected as a change in an electrical signal.
An example of the mechanical quantity sensor described above is a triaxial acceleration sensor using piezoresistive elements. The triaxial acceleration sensor using the piezoresistive elements includes a weight part, a flexible part connected to the weight part, a support part connected to the flexible part, and a plurality of piezoresistive elements arranged on the flexible part and detecting a displacement of the weight part in triaxial directions of XYZ. When an acceleration is applied to the sensor, the weight part is displaced, and the flexible part bends according to the displacement of the weight part. When the flexible part bends, the stress applied to the piezoresistive elements is changed, thereby changing the resistance values of the piezoresistive elements. By electrically detecting the changes of these resistance values, the acceleration applied to the acceleration sensor can be detected.
In general, as a package of the acceleration sensor, a ceramic package, a QFN Quad Flat None-Leaded) package, or a COB (Chip on Board) package is adopted. For example, Japanese Patent Laid-open No. 2007-322160 discloses an acceleration sensor element packaged with a case manufactured of alumina.
When a ceramic package is used, there is a problem such that a mold, a jig, a mask, and an original plate for screen printing are required to manufacture a package main body and a lid, thereby incurring increase in cost. Furthermore, when a control IC or the like is provided from a third party and a sensor is customized according to the provided control IC and packaged with the provided control IC, there is a problem such that there is a need to change the arrangement of a pin connect for connecting the control IC and the sensor and the design of the wiring pattern and others, thereby a package according to the product must be newly manufactured. In this case, a new mold and others suitable for the product are required, which causes an increase in manufacturing cost. Moreover, when a chip covered with a ceramic package is mounted on a substrate using an organic material (an organic substrate) such as a printed board, there is a problem such that, since the ceramic and the substrate have different coefficients of thermal expansion, reliability of a joint between the substrate and the package is decreased and reliability of the apparatus is also decreased. These problems occur also in the case as described in Japanese Patent Laid-open No. 2007-322160 in which alumina is used for packaging.
When any of a QFN package and a COB package is used, the entire components including the sensor, the control IC, and the substrate are required to be sealed with resin. Here, if the resin enters a space such as the weight part of the sensor, there is a problem such that the sensor does not function as a sensor, thereby decreasing reliability of the sensor. To address the problem, a barrier is required so as to prevent the resin from entering the sensor. However, there is a problem such that the number of processes for manufacturing increases in order to create the barrier and manufacturing cost increases accordingly. Also, in the case of the QFN package, as with the ceramic package, when a sensor is customized according to a control IC provided from a third party and packaged with the control IC, there is a problem such that there is a need to change the arrangement of a pin connect for connecting the control IC and the sensor and the design of the wiring pattern and others, thereby a package according to the product must be newly manufactured. As a result, the manufacturing cost increases. Still further, when the sensor is customized according to the control IC provided from the third party and packaged with the control IC, a relay substrate may be newly added to connect the control IC and the sensor. In this case, there is also a problem such that a package is required to be newly manufactured according to the arrangement of a pin connect of the relay substrate, thereby increasing manufacturing cost.
Still further, when any of the QFN package and the COB package is used, there is also a problem such that, when resin sealing is hardened, a stress is applied to the sensor in the sealing resin, thereby changing sensor characteristics. For example, when an acceleration sensor is used as a sensor, a change in offset voltage of the sensor changing according to the influence of the stress applied to the sensor at the time of sealing with resin is written in the control IC as a correction value. However, this correction range varies depending on the control IC. When the correction range of the control IC is narrow, a problem such that a shift in offset voltage due to the stress exceeds the correction range writable in the control IC and the sensor cannot function as a sensor.